Electromagnetic horn



G. ZEININGER ELECTROMAGNETIC HORN Oct. 22, 1935.

Filed Aug. ll, 1930 Patented Oct. 22 .1935

PATENT OFFICE ELECTROMAGNETIC nonN Gustav Zeininger, .Oberesslingen,Germany, as-

signor to Robert Bosch Aktiengesellschaft,

Stuttgart, Germany Application August 11, 1930, Serial No. 474,596

In Germany August 31, 1929 3 Claims. (CI- 177-,7)

' .The present invention relates to electro magnetic horns moreparticularly for motor vehicles.

- The object of the invention is a simple construction which is easilymanufactured and. 5 which, in spite of its simplicity produces a musicaland penetrating tone which is retained even when the horn has-been inuse for a considerable time. For this purpose the electromagneticarmature is secured to the diaphragm in known manner and a furtherjguidefor the armature is omitted. If however a simplified horn of this kindis to give a musical tone care must be taken by suitable means that thearmature rocks substantially in the same manner as if it were guided attwo places so that the armature cannot move into an inclined position orbe struck on I one side by the electro-magnet causing forces to act onthe diaphragm which tend to make the diaphragm bend into a positionotherthan that parallel to its position of rest.

This is obtained according to the invention in' that the flux passinginto the armature at its end passes out of it into a yoke forming aclosed flux path, which yoke lies considerably nearer the diaphragm thandoes the free end of the armature. v

One form of the construction of the invention is shown by way oi!example in the accompanying drawing in which: Figure l is a partsectional view on the line AB 01 Figure 2 and e Figure 2 is a partsectional view on the line CB oi Figure 1.

The casing of the horn consists of two metal parts a and b between theflanges of which is stretched a diaphragm c at its edges: A circularcorrugated metal plate e is secured tothe diaphragm c by a nut (Itogether with a.cylindrlcal armature f. The armature f has a flat end,40 the distance of which from the diaphragm in this example is about.222 of the diameter .of the diaphragm, and the diameter of which isabout a sixth of the diameter of the diaphragm. During operation of thehem, this end abuts against the end of a magnet core g which is alsofiat. The armature is mounted on the diaphragm with a surface whichamounts to about @222 of the diameter of the diaphragm. The magnet corea has mounted on it a magnet coil h, and together with an iron disc i isriveted to the base of the casing lid a. The armature f and the core 9have radial longitudinal slots lc so that there is low eddy currentloss.

Welded to the base of the casing lid a is U-shaped iron flux path yoke lwhich member enshrouds the magnet and completes the iron path from themagnet core to the armature. Ii centre opening for the armature isprovided in the web part of the iron yoke l and adjacent to this centreopening is a lateral recess for an I interrupter spring m. The armature,f is provided with an annular groove 11 at the place where it passesthrough the flux yoke l and the part lying between this groove and thediaphragm is increased in diameter to form a flange which is 10separated from the flux yoke l by an air gap greater than the air gapbetween the end of the armature and the core g and serves to operate theinterrupter spring m. The air gap between the flange and the flux yokeis smaller 15 than that between, the annular groove and the flux yoke sothat the flux path between the armature and the guiding member is in anaxial direction.

As the magnetic flux passes over the iron disc 10 i to the guidingmember I the casing of the horn can consist of relatively thin metal andif desired the iron disc can be disposed externally of the casinginstead of inside the casing-as shown.

It will be seen that a horn structure hasbeen provided in which thearmature is secured at one end to and supported solely by the diaphragm,and that yoke member 1 provides a return path for the magnetic fluxpassing out from the free end of the armature and into theelectromagnet, said flux being returned to the end of the armature nearthe diaphragm.

The construction described makes it possible to obtain a satisfactoryguiding of the armature and of thediaphragm which is important forobtaining a uniform tone.

If, for example, during the operation of the horn the diaphragm isoverstressed through any reason so that it endeavours to assume aninohhea position then this will be counterbalanced by the considerableleverage of the magnetic pull acting on the end of the armature.

By limiting the diameter of the end, tilting moments which can occurbetween the end and thi' core of the electromagnet are limited,similarly the carry over point of the flux from the armature to themagnet yoke is moved forward in the same sense from the end of thearmature to the diaphragm. On the other hand, the ample seating surfaceof the armature on the 'dia- 50.

phragm prevents the armature from assuming an inclined position on it.The diaphragm will therefore endeavour to maintain its normal positionand the striking of the armature against the core of the magnet beingthus maintained unii l ronic-met, 'a u-shapedjmetalryoke' tiallyenshrouding the armature to'Iorm therewith a, closed flux path andhaving an towards the armature located nearer to media-- phra'gmthan-the: free 'end'ot them-mature, andan iron plate bridgemagnetically. connecting the ends of the yoke and :saidelectro-magnecand secured to*the*cover of the casing to the same and provide a.mounting for saidelec tromagnet, whereby the magnetic flux passing fromthe treeendpg the armature andinto the electromagnet is returned to, thearmature by said yoke at apoint nearer-to the than the Ireeend ofsaidarmature. V w

2. An electromagnetic horn comprising in combinationa p'ot casing havinga magnetic bottom, a diaphragm secured at its periphery to the open endof said casi 8- magnetic-armature secured at one end to and supportedsolely byrsaid dia-.

'phragnr and extending at right angles thereto, an electromagnet securedto said bottom in alignment with said magnetic armature, a magneticU-shaped yoke member mounted insaid casing with its arms in engagementwith said magnetic bottom and its loop extending toward said diaphragm,said yoke member being provided with an aperture in its web portionthrough which said armature extends to provide an air gap between saidyoke member and said armature.

"3. An electromagnetic horn comprising in combination a pot casinghaving a magnetic plate in the bottom thereof, a diaphragm secured atits to the open end of said casing, a magne'tic armaturelsecured at oneend to and supported soleiy'by said diaphragm and extending at rightangles thereto,- an 'electromagnet including 7 a coil and a coresecuredto said magnetic plate with the core presenting a surface in alignmentwith an end suriace of said armature, a magnetic 20 U-shaped yoke membermounted in said casing with its arms in engagement'with said-magneticplate and its, loop extending toward said diaphragm, said yoke memberbeing provided with an aperture in its web portion through which said 25armature extends to provide an air gap between said yoke member and saidarmature.

GUSTAV 'ZEININGER.

